Spreng will join the firm in April from media group SMG - the former Scottish Media Group - where he has been comms director for almost a decade.
At ProStrakan he will be responsible for strategic comms with the group's investors, City analysts, specialist press and staff.
ProStrakan CEO Dr Wilson Totten said: ‘ProStrakan has grown very quickly and we reached a point in the group's development where communication is becoming increasingly important.'
Totten described Spreng as ‘one of Scotland's most experienced corporate communicators'.
Spreng, who will report to chief financial officer Adrian Gardner, said: ‘The ProStrakan management is ambitious and we share the same view on the role that communications should play in the group's future.'
He has not previously worked in the pharma sector, but said: ‘Each sector has its idiosyncrasies but a lot of similar corporate comms issues exist across all business sectors.'
Prior to SMG, which he joined in 1998 (PRWeek, 7 August 1998), Spreng was head of comms at General Accident. Before that he held positions at South of Scotland Electricity Board and Dunfermline Press.
ProStrakan's HQ is at Galashiels. EU-wide sales and marketing of its products are handled by commercial subsidiaries in the UK, France, Germany and Spain.
The company, which floated in 2005, uses Financial Dynamics for City comms and Medicom Group and Huntsworth Health for product comms.
SMG is yet to decide if it will replace Spreng.